CN114818364A - Bipolar direct current cable frequency-dependent RLC modeling method based on head wave valley amplitude-frequency characteristic fitting - Google Patents
Bipolar direct current cable frequency-dependent RLC modeling method based on head wave valley amplitude-frequency characteristic fitting Download PDFInfo
- Publication number
- CN114818364A CN114818364A CN202210534216.0A CN202210534216A CN114818364A CN 114818364 A CN114818364 A CN 114818364A CN 202210534216 A CN202210534216 A CN 202210534216A CN 114818364 A CN114818364 A CN 114818364A
- Authority
- CN
- China
- Prior art keywords
- frequency
- rlc
- model
- dependent
- cable
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Images
Classifications
-
- G—PHYSICS
- G06—COMPUTING OR CALCULATING; COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F30/00—Computer-aided design [CAD]
- G06F30/20—Design optimisation, verification or simulation
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for AC mains or AC distribution networks
- H02J3/001—Methods to deal with contingencies, e.g. abnormalities, faults or failures
-
- G—PHYSICS
- G06—COMPUTING OR CALCULATING; COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F2113/00—Details relating to the application field
- G06F2113/04—Power grid distribution networks
-
- G—PHYSICS
- G06—COMPUTING OR CALCULATING; COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F2119/00—Details relating to the type or aim of the analysis or the optimisation
- G06F2119/02—Reliability analysis or reliability optimisation; Failure analysis, e.g. worst case scenario performance, failure mode and effects analysis [FMEA]
-
- H02J2103/30—
Landscapes
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Theoretical Computer Science (AREA)
- Computer Hardware Design (AREA)
- Evolutionary Computation (AREA)
- Geometry (AREA)
- General Engineering & Computer Science (AREA)
- General Physics & Mathematics (AREA)
- Power Engineering (AREA)
- Monitoring And Testing Of Transmission In General (AREA)
Abstract
The invention discloses a bipolar direct current cable frequency-dependent RLC (radio link control) modeling method based on head wave valley amplitude-frequency characteristic fitting, wherein equivalent RLC parameters are obtained by fitting a first wave trough of a line frequency-dependent model amplitude-frequency characteristic. The parameters calculated by the method provided by the invention can accurately reflect the fault current characteristics of the bipolar cable line frequency-dependent model, and simultaneously, the cable model is simplified so that the cable model can be used for rapid quantitative analysis. The equivalent parameters obtained by the method can accurately describe the fault current characteristics of the frequency-dependent model; the original data required by calculation is the inherent frequency characteristic of the frequency-dependent model, and the calculation is not required to be carried out based on the historical fault current data of a specific fault scene, so that the method has clear physical significance; the invention takes the parallel cable as a single-port network to extract the frequency characteristic, thereby avoiding the problem caused by line coupling; the equivalent RLC parameters obtained by calculation can be applied to various fault scenes, and the limitation of the application scenes of the calculation method is greatly reduced.
Description
Technical Field
The invention relates to the technical field of fault current characteristic analysis, in particular to a bipolar direct current cable frequency-dependent RLC modeling method based on head wave valley amplitude-frequency characteristic fitting.
Background
Increasingly sharp environmental problems make countries dedicated to the development of renewable energy sources, and high-voltage direct-current transmission is a key technology for solving the problem of energy consumption. With the progress of Modular Multilevel Converter (MMC) technology, the voltage class and the transmission capacity of the hvdc transmission technology have been significantly improved in recent years. On the other hand, the demand of offshore wind farms for development to open sea increases the application proportion of direct current cables in high voltage direct current power grids. Cables are less prone to failure than overhead lines, but are typically permanently failed once they fail. Therefore, the method has engineering significance for analyzing the fault characteristics of the cable.
The power transmission line model is divided into a centralized parameter model and a distributed parameter model, wherein the distributed parameter model comprises a Bergeron model (Bergeron model) and a frequency-dependent model, the frequency-dependent model takes the frequency-dependent characteristics of all parameters into consideration, and the power transmission line model is the electromagnetic transient model which describes the transient fault current characteristics of the power transmission line most accurately at present. However, the frequency-dependent model is too complex to be applied in quantitative analysis. The quantitative analysis usually uses a centralized parameter model, which can most accurately reflect the fault characteristics of the power grid. But the lumped parameter model is less accurate and the accuracy will drop further as the line length increases. Due to the fact that the frequency-dependent model is too complex, fault current quantitative analysis is difficult to conduct. For fast quantitative analysis, it is necessary to obtain equivalent RLC parameters that can accurately reflect the line fault characteristics. Therefore, how to combine the advantages of the frequency-dependent model and the lumped parameter model to establish a lumped parameter model capable of accurately reflecting the frequency-dependent characteristics, and further, analyzing the fault current characteristics is a current challenge.
The prior art scheme is as follows:
measure 1: taking the mean of the polar and zero mode R-L parameters for approximate calculation, reference may be made to the following references:
approximation calculation method for short-circuit fault current of direct-current transmission network line of MMC (modular multilevel converter) in Toronto, Dongfuxi [ J ]. report on Chinese Motor engineering, 2019, 39 (2): 490-498.
And 2, measure 2: the method of fitting the historical fault current data by the least squares method can be referred to the following references:
shu Yongjie, Luyu, Deng Wei Cheng, Zhao Cheng Yong, the DC grid fault current calculation method and experimental verification using the overhead line equivalent model [ J ] China Motor engineering newspaper 2020,40(23): 7530-.
The disadvantages of the above measures:
the method has the following disadvantages: aiming at the problem of line coupling, a method of taking the average value of R-L parameters of a polar mode and a zero mode is directly adopted to carry out approximate calculation, and the calculation result has larger error.
The measure 2 has the disadvantages that: the least square method is adopted for parameter fitting based on specific historical fault current data, the method does not start from the attribute of the frequency-dependent model, physical significance is lacked, and the application scene is limited by the fitting scene.
Disclosure of Invention
In view of the above problems, an object of the present invention is to provide a method for modeling a bipolar dc cable frequency-dependent RLC based on fitting of the amplitude-frequency characteristics of the head-wave valley, wherein equivalent RLC parameters are obtained by fitting the first wave trough of the amplitude-frequency characteristics of a line frequency-dependent model, so as to accurately reflect the fault current characteristics of the cable line frequency-dependent model, and simplify the cable model so that the cable model can be used for rapid quantitative analysis.
The technical scheme is as follows:
a bipolar direct current cable frequency-dependent RLC modeling method based on head wave valley amplitude-frequency characteristic fitting comprises the following steps:
step 1: RLC equivalent model conversion
In order to obtain the amplitude-frequency response when two lines are connected in parallel, a large resistor is connected in series between the two lines of the power transmission line frequency-dependent model, then the power transmission line frequency-dependent model is replaced by an RLC equivalent model, and the specific parameters are explained as follows:
in the formula, s is Laplace operator; r, L and C are respectively the resistance, inductance and capacitance of the transmission line RLC equivalent model in unit length; l is the length of the transmission line; z π (s) is the transmission line impedance, Y π And(s) is the transmission line admittance to the ground, and both are frequency-variable parameters.
The equivalent model seen from the port is:
in the formula, Z cable The resulting bipolar cable impedance is seen for single port; r is the resistance of the large resistors connected in series;
step 2: RLC parameter solving
The method comprises the following steps of sweeping frequency of a single-port network, adopting a frequency domain near a first wave trough as a fitting frequency domain according to a frequency sweeping result, and adopting a least square method to perform fitting calculation, wherein the specific formula is as follows:
wherein f is a function expression of s, and R, L and C are RLC parameters to be solved and respectively correspond to the resistance, the inductance and the capacitance of a unit length;
is a least square method objective function; m is the sample size of the fitting frequency domain, and i represents the ith sample; y is i Is a frequency-dependent model frequency domain response; s i The corresponding laplacian operator is the ith sample.
The invention has the beneficial effects that: compared with the frequency-dependent model, the error of the simulation fault current of the equivalent RLC parameters finally obtained by the method can be lower than 5%, and the equivalent parameters obtained by the method can accurately describe the fault current characteristics of the frequency-dependent model. Secondly, the original data required by the calculation is the natural frequency characteristic of the frequency-dependent model, the calculation is not required to be carried out based on the historical fault current data of a specific fault scene, and the method has a clear physical meaning. In addition, the invention takes the parallel cable as a single-port network to extract the frequency characteristic, thereby avoiding the difficult problem brought by line coupling. Finally, the equivalent RLC parameters obtained by calculation can be applied to various fault scenes, and the limitation of the application scenes of the calculation method is greatly reduced.
Drawings
Fig. 1 is a model of a bipolar transmission line considered a single port network; the RLC equivalent model is converted according to the frequency model.
Fig. 2 shows the results of a single-port network sweep.
Fig. 3 shows the amplitude-frequency characteristics of the frequency-dependent model using RLC fitting.
Fig. 4 is a power transmission line configuration based on a frequency dependent model.
FIG. 5 shows the amplitude-frequency characteristics of the RLC equivalent parameter fitting cable according to the frequency model.
Fig. 6 is a comparison of frequency-dependent model and RLC fault current in a symmetric unipolar interpolar short circuit fault scenario.
FIG. 7 is a comparison of frequency dependent model and RLC fault current for a symmetric unipolar single-pole ground short fault scenario.
Detailed Description
The invention is described in further detail below with reference to the figures and specific embodiments.
The invention solves the equivalent RLC parameters based on the amplitude-frequency characteristic fitting of the frequency-dependent model. The left part of fig. 1 is a frequency dependent model of a bipolar dc transmission line, which is considered as a single port network. In order to obtain the amplitude-frequency response when the two lines are connected in parallel, a large resistor r is connected between the two lines in series.
The frequency dependent model in the left part of fig. 1 is replaced by an RLC equivalent model, the result is shown in the right part of fig. 1. The parameters are explained as follows:
in the formula, s is Laplace operator; r, L and C are respectively the resistance, inductance and capacitance of the transmission line RLC equivalent model in unit length; l is the length of the transmission line; z π (s) is the transmission line impedance, Y π And(s) is the transmission line admittance to the ground, and both are frequency-variable parameters.
The equivalent model seen from the port is:
sweeping the single-port network of fig. 1 may result in the sweeping results shown in fig. 2.
The amplitude-frequency characteristic of the RLC equivalent model only has one wave trough, and at most, only the first wave trough of the frequency-dependent model can be fitted, so that the frequency domain near the first wave trough is used as a fitting frequency domain, and the fitting frequency domain with the largest influence on the fault characteristic is adopted. Fitting calculation is carried out by adopting a least square method, and the specific formula is as follows:
in the formula, f is a function expression of s, R, L and C are unknown parameters, and the objective is solved;
is a least square method objective function; m is the fitted frequency domain sample size, and i represents the ith sample. Equation (3) aims to find a set of cable equivalent concentration parameters R, L and C so that the frequency-dependent model frequency domain response yi is squared with the difference between the equivalent line impedance expression f (si), that is, the equation
And minimum.
The fitting result is shown in fig. 3, and it can be seen that the RLC model can better fit the amplitude-frequency characteristic of the first trough of the frequency-dependent model. The RLC equivalent parameters calculated by the method are based on the natural frequency response of the cable frequency-dependent model, have physical significance, and can accurately describe the fault characteristics of the cable frequency-dependent model.
Example (b):
the cable of the PSACD/EMTDC calculation example is selected as an example for explanation. FIG. 4 is a schematic diagram of a cable configuration, with the radius data for each layer of the cable shown in Table 1; the resistivity of the ground surface is 100. omega. m.
TABLE 1 Cable model geometry
And for the fault characteristics of the equivalent model, verifying the double-end symmetrical unipolar direct-current power grid, and setting the faults as an inter-electrode short-circuit fault and a unipolar grounding fault. The parameter configuration of the symmetric single-pole power grid MMC is shown in the table 2, and in the table 2, Larm represents the bridge arm inductance of the MMC; CSM represents MMC submodule capacitance; RON represents the conduction resistance of the MMC sub-module; NSM represents the number of bridge arm sub-modules of the MMC; rg and Lg respectively represent grounding resistance and grounding inductance when the star-shaped reactance at the MMC valve side is grounded through a resistor. The large resistance r in series between the two lines when the equivalent RLC model is obtained is set to 1M Ω.
TABLE 2 symmetrical monopole double-ended DC grid parameters
The verification scheme comprises the following steps:
the method provided by the invention is used for calculating the equivalent parameters of the cable. After a lot of data verification, the best fit frequency range is 317-387Hz, and the fitting result is shown in FIG. 5.
Fig. 5-7 are comparison of frequency-dependent model and equivalent RLC fault current simulation results under different fault scenarios. Therefore, under different fault scenes, the equivalent RLC parameters can correctly describe the fault characteristics of the frequency-dependent model, and the error is small.
In summary, the equivalent RLC modeling method of the cable provided by the invention calculates the equivalent RLC parameters based on the inherent amplitude-frequency characteristics of the cable frequency-dependent model. The established model can accurately describe the cable fault current characteristics including the fault current rise rate and the like. The original data required by calculation is the inherent frequency characteristic of the frequency-dependent model, the coupling problem among power transmission lines does not need to be considered, the calculation is not needed based on the historical fault current data of a specific fault scene, the method has clear physical significance and high accuracy, and can be applied to different types of power grid fault analysis scenes.
Claims (1)
1. A bipolar direct current cable frequency-dependent RLC modeling method based on head wave valley amplitude-frequency characteristic fitting is characterized by comprising the following steps:
step 1: RLC equivalent model conversion
In order to obtain the amplitude-frequency response when two lines are connected in parallel, a large resistor is connected between the two lines of the bipolar direct current transmission line frequency-dependent model in series, then the transmission line frequency-dependent model is replaced by an RLC equivalent model, and the specific parameters are explained as follows:
in the formula, s is Laplace operator; r, L and C are respectively the resistance, inductance and capacitance of the transmission line RLC equivalent model in unit length; l is the length of the transmission line; z π (s) is the transmission line impedance, Y π (s) is the transmission line admittance to the ground, both of which are frequency-varying parameters;
the equivalent model seen from the port is:
in the formula, Z cable The resulting bipolar cable impedance is seen for single port; r is the resistance of the large resistors connected in series;
step 2: RLC parameter solving
The method comprises the following steps of sweeping frequency of a single-port network, adopting a frequency domain near a first wave trough as a fitting frequency domain according to a frequency sweeping result, and adopting a least square method to perform fitting calculation, wherein the specific formula is as follows:
wherein f is a function expression of s, and R, L and C are RLC parameters to be solved and respectively correspond to the resistance, the inductance and the capacitance of a unit length;
is a least square method objective function; m is the sample size of the fitting frequency domain, and i represents the ith sample; y is i Is a frequency-dependent model frequency domain response; s i The corresponding laplacian operator is the ith sample.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210534216.0A CN114818364B (en) | 2022-05-17 | 2022-05-17 | Bipolar direct current cable frequency-dependent RLC modeling method based on head wave valley amplitude-frequency characteristic fitting |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210534216.0A CN114818364B (en) | 2022-05-17 | 2022-05-17 | Bipolar direct current cable frequency-dependent RLC modeling method based on head wave valley amplitude-frequency characteristic fitting |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN114818364A true CN114818364A (en) | 2022-07-29 |
| CN114818364B CN114818364B (en) | 2023-03-14 |
Family
ID=82514981
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202210534216.0A Active CN114818364B (en) | 2022-05-17 | 2022-05-17 | Bipolar direct current cable frequency-dependent RLC modeling method based on head wave valley amplitude-frequency characteristic fitting |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN114818364B (en) |
Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20120019964A1 (en) * | 2010-07-23 | 2012-01-26 | Xantrex Technology Inc. | Photovoltaic bipolar to monopolar source circuit converter with frequency selective grounding |
| CN108920791A (en) * | 2018-06-21 | 2018-11-30 | 南方电网科学研究院有限责任公司 | A modeling method and model of a power electronic switch |
| CN110108986A (en) * | 2019-05-29 | 2019-08-09 | 华北电力大学 | DC grid fault current complex frequency domain calculation method |
| CN110535348A (en) * | 2019-09-03 | 2019-12-03 | 华北电力大学 | Modeling Method of High Frequency Impedance of DC Converter |
| CN111245002A (en) * | 2020-03-02 | 2020-06-05 | 武汉大学 | MMC-based double-pole flexible direct-current power grid short-circuit and ground fault current prediction method |
| CN113595044A (en) * | 2021-07-30 | 2021-11-02 | 四川大学 | Method for evaluating influence of direct-current power grid topology on fault current |
| CN113922408A (en) * | 2021-09-30 | 2022-01-11 | 合肥工业大学 | MMC-HVDC power grid bipolar short-circuit fault current calculation method based on parameter inversion |
-
2022
- 2022-05-17 CN CN202210534216.0A patent/CN114818364B/en active Active
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20120019964A1 (en) * | 2010-07-23 | 2012-01-26 | Xantrex Technology Inc. | Photovoltaic bipolar to monopolar source circuit converter with frequency selective grounding |
| CN108920791A (en) * | 2018-06-21 | 2018-11-30 | 南方电网科学研究院有限责任公司 | A modeling method and model of a power electronic switch |
| CN110108986A (en) * | 2019-05-29 | 2019-08-09 | 华北电力大学 | DC grid fault current complex frequency domain calculation method |
| CN110535348A (en) * | 2019-09-03 | 2019-12-03 | 华北电力大学 | Modeling Method of High Frequency Impedance of DC Converter |
| CN111245002A (en) * | 2020-03-02 | 2020-06-05 | 武汉大学 | MMC-based double-pole flexible direct-current power grid short-circuit and ground fault current prediction method |
| CN113595044A (en) * | 2021-07-30 | 2021-11-02 | 四川大学 | Method for evaluating influence of direct-current power grid topology on fault current |
| CN113922408A (en) * | 2021-09-30 | 2022-01-11 | 合肥工业大学 | MMC-HVDC power grid bipolar short-circuit fault current calculation method based on parameter inversion |
Non-Patent Citations (4)
| Title |
|---|
| MD. SAIFUL ISLAM等: "Design and Implementation of IGBT Based High Frequency Output Cyclo-Inverter Prototype", 《网页在线公开：HTTPS://IEEEXPLORE.IEEE.ORG/STAMP/STAMP.JSP?TP=&ARNUMBER=8679254》 * |
| 唐昆明等: "基于RLC模型参数辨识的配网电缆单相接地故障的单端时域测距方法", 《电力系统保护与控制》 * |
| 王子文等: "柔性直流电网潮流转移特性及安全运行影响分析", 《电力系统保护与控制》 * |
| 郝亮亮等: "MMC-HVDC电网输电线路双极短路故障电流的实用计算", 《电力系统自动化》 * |
Also Published As
| Publication number | Publication date |
|---|---|
| CN114818364B (en) | 2023-03-14 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN111308264B (en) | Power distribution network single-phase earth fault section positioning method based on cosine similarity | |
| CN108663602B (en) | Method and system for single-pole fault line selection and segment location in flexible DC distribution network | |
| CN108647396B (en) | Key equipment fault risk assessment method for improving reliability of converter valve | |
| CN108512201A (en) | A kind of multiterminal flexible direct current power grid DC line fast protection method and system | |
| CN108879664B (en) | AC/DC system online voltage stability evaluation method based on wide area measurement | |
| CN111381129B (en) | Ground fault line and type identification method and device based on ultralow frequency signal | |
| CN111856322A (en) | Method and device for accurate location of bipolar short-circuit fault in DC distribution network based on MMC | |
| CN114465211B (en) | Flexible line circuit protection method and system based on flat wave inductance voltage head wave time | |
| CN115184718B (en) | Three-core cable fault positioning method based on time domain analysis | |
| CN113376477A (en) | Flexible direct-current power grid single-end protection method based on traveling wave energy spectrum matrix similarity | |
| CN118348362B (en) | A method for detecting high-resistance faults in distribution networks based on quadratic coefficients of fitting curves | |
| CN115117866B (en) | Single-ended line protection method for flexible DC power grids based on time-domain voltage traveling waves | |
| CN113358978B (en) | Fault type identification method and device for single-phase fault in distribution network | |
| CN112904233B (en) | Ground fault positioning method and device based on ground wire current reactive component | |
| CN118244053A (en) | Transmission line fault location method, system, storage medium and electronic device based on traveling wave front fitting | |
| CN106227912A (en) | Obtain and simplify the analysis method of maximum transient overvoltage under wind energy turbine set cable system asymmetry short circuit fault | |
| CN109188205A (en) | A kind of distance measuring method of the distance protection based on petal type power grid | |
| CN112039108A (en) | Fast Estimation Model and Calculation Method for Single-Ended Transient Response of HVDC Transmission System | |
| CN114818364A (en) | Bipolar direct current cable frequency-dependent RLC modeling method based on head wave valley amplitude-frequency characteristic fitting | |
| CN113358979B (en) | A phase selection method and phase selection device for single-phase disconnection fault in distribution network | |
| CN112444756B (en) | A Small Current Ungrounded Wire Selection Method Based on Coupling Ellipse Distribution Characteristics of Zero-sequence Power Frequency Electrical Components | |
| CN113721115A (en) | Single-phase earth fault positioning method for neutral point flexible-earthing power distribution network | |
| CN109375034A (en) | A method for obtaining the DC component of short-circuit current in a power system branch | |
| CN117031193A (en) | Extra-high voltage three-terminal hybrid direct current transmission line waveform characteristic fault region discrimination method based on deep learning | |
| CN110208655A (en) | A kind of one-phase earthing failure in electric distribution network model analysis method under grounding through arc mode |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |